advice on next build

[Glenn]

Hi: I was wondering if there are any alternatives amps for a 4xel84 power section that I was contemplating for my next build.
I have a 4xel84 pre drilled chassis withe 3 pre amp tube sockets.
I also have a 270HX - 275 0 275 with i think 230mA and 6 amps for the 6.3volt taps - I also have an Edcor 5.2 k 35 watt OT

I just built a Trainwreck Rocket type amp and its great amp, and I was going to build a Liverpool with the above, but i was wondering if there are any other alternatives amp designs?
From what i read and heard the Liverpool is more friendly to a single coil guitar, and I love my Les Paul
the Rocket is like an AC30 so that's out.... from what I can tell 
I like something with good overdrive
the reason I ask, is because this forum has alot of different alternatives and before I start building there might be something different?
thanks, Glenn

[tubenit]

Just an idea to consider and I am not saying you "should" build this.

What about a HoSo 56 using the 5879 for V1 and the power section being two EL84's cathode biased with two 6V6's cathode biased.

With respect, Tubenit

[shooter]

an off the wall, I built a quad-SE as a quazi HIFI but you could mate any pre n tweak to taste

[Glenn]

thanks Guys. Maybe i can look into incorporating the hoso v2 12ax7 and v1 5879 into a Liverpool.
or just build a 30 watt Hoso, with a PPMIV. I built an attenuator and it works well, as I only play in my basement
I have been listening to the soundclips of the hoso56 in the soundclips section
thanks, Glenn

[tubenit]

 I drew up (quickly) the idea of the EL84 & 6V6 HoSo56.    Nice thing about this is you could remove either the pair of EL84's or 6V6's or leave them both in.

The ExpressSCH schematic has a 2nd page with a suggested B+ rail.  Check for errors in schematic.

Just an idea to consider.  Not pushing you to build it.  Just tossing it out there for anyone who might be interested?

With respect, Tubenit

[Glenn]

That's Awesome Tubenit. what you drew up quickly would take me months to do....

What is the purpose of the Mosfet?

also what would the difference be for using say one 10 watt 120 ohm bias resistor for a pair of power tubes ~ vs using 1 25 watt bias resistor (half value) for all 4 tubes if they are el84's?

thanks, Glenn

[DummyLoad]

What is the purpose of the Mosfet?

source follower - SS counterpart of a cathode follower. low Z output to drive the tone stack.

--pete

[92Volts]

With one shared resistor you can't remove a pair of tubes for reduced power output-- or run the amp with 2 tubes for any reason such as troubleshooting. Also, a loss of current through one tube decreases bias voltage, increasing current through others-- one failure becomes more likely to cause other failures.

Generally, you lose some of the protection/self-correction that cathode bias offers compared to fixed bias. In fact, tube datasheets recommend individual resistors for each of 2 tubes in a single push-pull pair for this reason though shared resistors are used all the time.

[kagliostro]

Note that 6V6 cathode resistor is 270R and EL84 is 130R

too different values to share a common resistor

Franco

[Glenn]

Thanks for that answer and lesson 92Volts.
I was thinking one cathode resistor might be an issue, if using 4 tubes. I will incorporate 1 resistor per 2 tubes.

kagliostro - yes i saw that, for 6v6... my chassis I want to use is punched for for 9 pin tube sockets, so I want to use all 9 pin tubes.
Also thanks dummyload, I still don’t quite get it but you gave me something to look up!

Thanks, Glenn

[tubenit]

so I want to use all 9 pin tubes.

Then you could use a pair of 6BM8 pentodes and not use the triode section which I have done with no problem for 7-9 watts AND
use a pair of EL84's for 18 watts.  IF your PT is 300-0-300 and you are using a 5Y3GT rectifier, then I think that could work for around 330 volts on the plates of each pair.   You'd need to check on data sheets max ratings on plates and grids for 6BM8.

And just as I suggested regarding a pair of 6V6's and a pair of EL84's,   use a separate cathode resistor and cap for each pair.  I never suggested a pair of 6V6's and a pair of EL84's share the same resistor.

With respect, Tubenit

[Glenn]

thanks Tubenit: I was just asking generally about cathode bias resistors. I have seen a single resistor used for 4 all the same tubes.
and have seen using 1 resistor for a pair of like tubes, sorry for any confusion.
I built and love my mini bassman with 6bm8's.
I have 4 el84's i want to use
thanks, Glenn